Enable the third sidebar sort mode — a freely defined order.
- api: `PATCH /pages/:id/position` (before/after neighbour) recomputes only
the moved page's fractional `sort_key`. Pure `sort-key.ts` helpers
(`nextKeyOrRebalance`, `evenlySpacedKeys`) decide between the cheap
single-key path and a full pond rebalance to evenly-spaced keys when a key
would exceed MAX_SORT_KEY_LENGTH or the client's neighbours are stale;
rebalance runs in one transaction. Order is server-authoritative.
- web: enable 'manual' in the sort-mode switch; in manual mode the owner can
reorder via native drag-and-drop (drop above/below by pointer half) or the
keyboard (per-row up/down buttons), each announced through an aria-live
region. Reordering is hidden while a label filter narrows the list. New
pages already append at the end (create uses generateKeyBetween(last, null)).
Pure `reorder.ts` neighbour helpers, unit-tested.
- i18n: manual sort mode + reorder strings (de + en).
- tests: sort-key property test (10.000 adversarial reorders never collide or
overflow — rebalance verified); reposition db test (persist, server-order,
sort-mode switch keeps manual order); reorder e2e pack (keyboard reorder
persists across reload + identical on a fresh read; aria-live announced).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PGdhRiwU1WRL4XxJfZYipY
